Electronic properties of amorphous and crystalline ge 2sb. Thermoelectric figure of merit of degenerate and nondegenerate. Yet in five decades the roomtemperature zt of bulk semiconductors. Applied sciences and engineering large, nonsaturating. Ferromagnetic semiconductors fmss featuring a high curie transition temperature tc and a strong correlation between itinerant carriers and localized magnetic moments are of tremendous importance for the development of practical spintronic devices. At low temperature the thermopower vanishes, as shown in fig.
In the third edition several topics are extended and treated in more depth including surfaces, disordered materials, amorphous semiconductors, polarons, thermopower and noise. All compounds are predicted and experimentally confirmed to be narrowbandgap ptype semiconductors with high seebeck thermopower values, up to 250. It is the ability to control conductivity that make semiconductors useful as currentvoltage control elements. Thenatureof thermopower in bipolar semiconductors yu.
Strategies for high thermoelectric zt in bulk materials. In 1834, a french watchmaker and part time physicist, jean peltier found that an electrical current would produce a temperature gradient at the. In this material, colossal values of the thermopower s amounting to several tens of mvk along with a huge power factor pfs2 of 2300wk2cm were observed at around 10k. Here, we report the thicknessmodulated band engineering of nanosheets based on semimetallic platinum diselenide ptse2 resulting in a thermopower. The main part of the book deals with the three important problems. Theoretical studies on the thermopower of semiconductors. Oct 17, 2014 the development of organic semiconductors for use in thermoelectrics requires the optimization of both their thermopower and electrical conductivity. Pdf effect of hydrogen implantation on semiconductor. Semiconductor science and technology rapid communication diffusion thermopower in graphene to cite this article. The seebeck coefficient also known as thermopower, thermoelectric power, and thermoelectric sensitivity of a material is a measure of the magnitude of an induced thermoelectric voltage in response to a temperature difference across that material, as induced by the seebeck effect. Electronic properties of amorphous and crystalline ge 2. It provides information about the interaction of electrons and phonons, impurities and other defects in a system. Giant thermopower of ionic gelatin near room temperature. Band gap estimation from temperature dependent seebeck.
Furthermore, the thermopower of gete and snte obviously exceeds the parabolic band model values obtained within csta at doping levels larger than 3. Local thermal magnetization fluctuations in lidoped mnte are found to increase its thermopower. For semiconductors, the electrons can jump from the valence orbits but does require a small amount of energy to free the electron from the atomic core. The nature of thermopower in bipolar semiconductors core. Conductivity can be varied by several orders of magnitude. Intraband conductivity and thermopower of semiconductors with. Large, nonsaturating thermopower in a quantizing magnetic field. Semiconductor and simple circuitsnot to be republished. Materials, devices and simple circuits semiconductors. The nature of thermopower in bipolar semiconductors by yu. Note log derivative not an extensive quantity multiplicative factors in density of states specific heat, entropy or in.
In order to better understand the variation in the transport properties as. Note that, in the present work, the thermopower, instead of hall voltages and optical timeof. Mar 15, 2020 as per theory of semiconductor, impure semiconductors are called extrinsic semiconductors. Depending on the type of impurity added we have two types of semiconductors.
The theory of thermopower with regard to the real boundary conditions at the metalsemiconductor interface and surface energyband bending in bipolar semiconductors is developed. The experimental data on thermoelectric semiconductors based on pbte, used for power generation applications near 500 c, and based on bi 2te 3 used. Types of doped semiconductors there are two different ways of adding an impurity to the semiconductor atom. Glaudell materials department and materials research laboratory, university of california santa barbara, santa barbara, ca, 931065050 usa. It is demonstrated that, in the case of strong degeneracy, quantum levels lying below the fermi level intersect the fermi level with an increase in the magnetic field, which leads to jumpwise oscillations of the. The latter compound shows carrier concentrations and mobilities, 1. Strong thermopower enhancement and tunable power factor. Thermoelectric properties of the incommensurate layered. This thesis explains the theory behind the seebeck e ect, describes the apparatus used to measure seebeck coe cient at room temperature, presents experimental values of sc for common alloys, metals, semiconductors and discusses the results of the experiment. Chapter 3 thermopower and mobility in inn heterostructures.
Nonetheless, we are unaware of any experiments that demonstrate the b 2 enhancement of s xx implied by eq. Kotliar 1department of physics and astronomy, rutgers university, piscataway, new jersey 08854, usa 2nanosystem research institute, aist, tsukuba 3058568, japan. Semiconductors are known to have high seebeck coe cient values. Logvinov teacher training university, avenue krivonosa 2, ternopol 282009, ukraine o. Basics of semiconductor devices indian institute of. The types of doped semiconductors formed after the addition of the impurity are. Electronic band engineering is a promising approach to enhance the thermopower of thermoelectric materials. The oxide semiconductor zno is an ideal target material for experimentally examining the relationship between the 2d density of states and the seebeck effect. If both types of dopants are present, the one present in higher concentration determines the type of the semiconductor.
Bulk 3d zno has a nondegenerate and simple conductionband structure with a parabolic energy dispersion around the conduction band minimum. Semiconductors can exhibit either electron conduction negative thermopower or hole conduction positive thermopower. The transparent oxide semiconductor tos with large bandgap e g. Request pdf theoretical studies on the thermopower of semiconductors and lowbandgap crystalline polymers a numerical procedure has been used for the prediction of the seebeck coefficient of.
Realization of large thermopower using semimetals and narrowgap semiconductors in a magnetic field. A numerical procedure has been used for the prediction of the seebeck coefficient of a crystalline material based on its electronic band. Jun 03, 2010 thermopower of correlated semiconductors. Giant thermopower and gure of merit of semiconducting. Thermoelectric materials are vital for the development of thermoelectric generators and coolers used in manufacturing processes. Under optimal doping, s is predicted to increase by 30 times, and s2. Often the measurement of resistivity or conductivity is inadequate in distinguishing among different scattering mechanisms and the thermopower can then be used as a sensitive probe of transport properties since it provides complementary infor. Pdf validity of the rigid band approximation in the study. Thermopower of correlated semiconductors rutgers physics. Enhancement in thermopower in singlecrystal bi2te3. Paramagnon drag in high thermoelectric figure of merit li.
In this chapter, we will restrict ourselves to the study of inorganic semiconductors, particularly. Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature. Heavily doped semiconductors in this subsection, we present a calculation of the thermopower s xx. Isbn 9781402064807 hb isbn 9781402064814 ebook published by springer. Temperature and magnetic dependence of the resistance and thermopower in the topological insulator bi1 xsb x nanowires albina nikolaeva,1,2,leonidkonopko1,2,titohuber,3,ivanpopov2,pavel bodiul2,andevghenii moloshnik2 1ghitu institute of electronic engineering and nanotechnologies, asm, academiei str. Theoretical studies on the thermopower of semiconductors and low. The thermopower of an insulator often decreases with temperature. Proceedings of international workshop on physics of semiconductor devices. Thermodynamic basis of thermopower in metals and semiconductors. Impact of the doping method on conductivity and thermopower in semiconducting polythiophenes anne m. To be competitive compared with conventional refrigerators and generators, one must develop materials with zt 3. Chapter 3 thermopower and mobility in inn heterostructures 3.
The thermopower for different carrier types is given by a weighted average to their electrical conductivity values. In this study, we measured s of ladoped basno 3 films with varied carrier concentration and basno 3 with tft structure, in which carrier concentration can be modulated by applying the. Apr 24, 2020 the high thermopower in the irmnbased device demonstrated in this work is an important step toward fulfilling the needs of ultralowpower iot applications 40. T and the electrical field e in a conducting material, where the net current through the sample is zero see boltzmann equation and scattering mechanisms, thermoelectric power.
Resonant level enhancement of the thermoelectric power of. For two materials of current interest, feas2 and fesb2, we compute the electronic structure and thermopower. The seebeck coefficient of a highly doped osc, which consequently displays a high power factor, is only on the order of 10s of. Band structures of the semiconductors and semiconductor compounds of interest are also considered. Thermopower modulation clarification of the intrinsic. Catalogue record for this book is available from the library of congress. Thermopower, tp, which is sensitive to the composition and structure of the system, is an interesting and important transport property for study in finite qw structures. Thermopower modulation clarification of the operating.
Resonant levels in bulk thermoelectric semiconductors. It is shown that, for some values of the surface parameters and sample thickness, the surface potential can substantially affect the magnitude of the thermopower. Thermopower of a semiconductor film with parabolic. Kotliar 1department of physics and astronomy, rutgers university, piscataway, new jersey 08854, usa 2nanosystem research institute, aist.
Engineering the thermopower in semiconductor molecule junctions. Click download or read online button to get ferroelectric semiconductors book now. Within a sufficiently high magnetic field, a large enhancement of the electronic density of states and a reduction in the fermi energy occurs. Seebeck coefficient an overview sciencedirect topics. Related content role of charged impurities in thermoelectric transport in molybdenum disulfide monolayers. Thermoelectric devices create a voltage when there is a different temperature on each side. Temperature and magnetic dependence of the resistance and. The seebeck coefficients generally vary as function of temperature and depend strongly on the composition of the conductor. Apr 30, 2020 harvesting heat from the environment into electricity has the potential to power internetofthings iot sensors, freeing them from cables or batteries especially for use as wearable devices. Realization of large thermopower using semimetals and narrow. The thermopower, or seebeck, coefficient s is defined as the coefficient in the relation. Dos in earthabundant semiconductors can be engineered to enhance thermoelectric thermopower and power factor. However, after 1990, a few semiconductor devices using organic semiconductors and semiconducting polymers have been developed signalling the birth of a futuristic technology of polymerelectronics and molecularelectronics. Lecture 18 semiconductors continued 3 physics 460 f 2006 lect 18 thermopower and peltier effect both electrons and holescontribute to conductivity and conduct heat the peltier effect is the generation of a heat current j u due to an electric current j q in the absence of a thermal gradient.
The physics of semiconductors requires little or no prior knowledge of solidstate physics and evolved from a highly regarded twosemester course. Intraband conductivity and thermopower of a unipolar semiconductor with a slowly varying gaussian random field are computed. Similarly, holes are the majority carriers in a semiconductor doped with acceptors and it is termed p type. This site is like a library, use search box in the widget to get ebook that you want. In semiconductors, achieving a thermopower of order k b e is relatively common, particularly when the donoracceptor states are shallow and the doping is light. The realization of such materials hinges on the ability to generate and manipulate a high density of itinerant spinpolarized carriers and the. These materials can save energy and money with heating processes. Sanchela1, takaki onozato2, bin feng3, yuichi ikuhara3 and hiromichi ohta1, 1research institute for electronic science, hokkaido university, n20w10, kita, sapporo 0010020, japan. In situations where phonons provide a dominant contribution to the thermal conductivity so that the wiedemannfranz law is strongly violated, one generically has k xx.
Thermopower modulation clarification of the intrinsic effective mass in a transparent oxide semiconductor, basno 3 anup v. Existing analyses require that a cross coefficient be determined empirically. Introduction to semiconductors and semiconductor devices a background equalization lecture reading. Ferroelectric semiconductors download ebook pdf, epub. Enhanced thermopower in zno twodimensional electron gas.
Effect of energyband bending on the thermopower in bipolar. Iiiv clathrate semiconductors with outstanding hole mobility. In 100 million parts of semiconductor one part of impurity is added. Recent years organic materials attract more and more attention of investigators as new materials with more diverse properties and lower cost in comparison with ordinary metals and semiconductors 1. Increasing demand for higher energy efficiency calls for waste heat recovery technology. S which rises linearly with temperature to a maximum. We investigated motts equation for the seebeck coefficient and found it to be inappropriate for nondegenerate semiconductors and partly correct for degenerate.
We find feas2 to be well described within densityfunctional theory and the therefrom deduced seebeck coefficient to be in quantitative. Thus, facilitating practical thermoelectric generation systems is strongly desired. The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. Thermopower has been used as a powerful tool to probe transport mechanisms in metals and semiconductors. Impact of the doping method on conductivity and thermopower. Lecture 1 introduction to semiconductors and semiconductor. Currentvoltage control is the key to switches digital logic including microprocessors etc, amplifiers, leds, lasers, photodetectors, etc. Such behavior is typical of doped semiconductors, and the maxima can be used to estimate8 the band gap, 0. Bratkovsky2 1department of physics, loughborough university, loughborough le11 3tu, united kingdom 2hewlettpackard laboratories, 1501 page mill road, palo alto, california 94304, usa received 5 march 2010.
Realization of large thermopower using semimetals and. Here the thermopower of a nondegenerate semiconductor \s 200 \mu vk\ is used where the thermopower again depends on the fermi level. Tk, where is the thermopower ors seebeck coefficient, is the electrical con. Unlike semiconductors, metals have low seebeck coe cient. Charge disproportionation triggers bipolar doping in fesb2. Room temperature seebeck coe cient measurement of metals and. The conventional electronicthermoelectric ete materials usually are narrowbandgap semiconductors that utilize the electrons or holes as the energy carriers.
The physics of semiconductors an introduction including. Pdf the thermoelectric figure of merit is calculated for a compound material comprising thin semiconductor and wider metallic layers. The magnetic field ensures that the transverse drift of both electrons and holes contribute additively to the thermopower. Particular usefulness comes from extracting transport functions from the seebeck coefficientconductivity relation, especially in doped semiconductors. Thermopower enhancement in conducting polymer nanocomposites via carrier energy scattering at the organicinorganic semiconductor interface ming he, a jing ge, a zhiqun lin, b xuhui feng, c xinwei wang, c hongbin lu, a yuliang yang a and feng qiu a. Extrinsic semiconductor is formed by adding a small amount of impurity. For a typical thermoelectric material, thermopower or seebeck coefficient is about 100 200. Tp, s has two contributions, namely, the diffusion tp, s d and phonon drag tp, s g. Pdf thermoelectric figure of merit of metalsemiconductor. Peltier effect in 1834, a french watchmaker and part time physicist, jean peltier found that an electrical. Thermodynamic basis of thermopower in metals and semiconductors guy, a. If a silicon or germanium atom in its pure form is doped with an element of group five in a small amount, such as antimony, arsenic or phosphorus, these elements having 5 electrons in their. Kotliar 1department of physics and astronomy, rutgers university, piscataway, new jersey 08854, usa. Relationships for the transverse magnetothermopower of a semiconductor film with parabolic potential are derived for the cases of nondegenerate statistics and strong degeneracy.
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